Engine starter drive



June 27, 1967 J, J, m 3,327,821

ENGINE STARTER DRIVE Filed Dec. 1'7, 1965 a 51 :20 to 60 I VENTOR. WITNESS: Jwnes M. 572772;. w g I 1/ ATTORNEY United States Patent O 3,327,821 ENGINE STARTER DREVE James J. Digby, Elmira, N.Y., assignor to The Bendix Corporation, a corporation of Delaware Filed Dec. 17, 1965, Ser. No. 514,599 6 Claims. (Cl. 19263) The present invention relates to engine starter drives of the inertia type and, more particularly, to an inertia type engine starter drive having one-way torque absorption, mesh enforcing and alignment capabilities.

It is an object of the present invention to provide an inertia type engine starter drive having self-alignment capability in order to prevent side loads on the engine shaft and bearings.

It is an object of the present invention to provide an inertia type starter drive having energy absorption in the start up mode of operation only.

It is an object of the present invention to provide an inertia type starter drive in which all the parts having a large mass are on the starter motor side of the drive.

It is a further object of the present invention to provide an inertia type starter drive which has a return spring and substantially no torque absorption for speedy disengagement.

It is a still further object of the present invention to provide a low cost, simple, and reliable inertia type engine starter drive.

Additional objects and advantages of the present invention will become apparent on consideration of the following description taken in conjunction with the accompanying drawing of an embodiment of the present invention in which:

FIGURE 1 is a view, partly in section, of an engine starter drive;

FIGURE 2 is a section view of the impact torque absorbing device taken along section lines 22; and

FIGURE 3 is a fragmentary view, partly in section, of the two part driven portion of the starter drive.

In FIGURE 1 there is illustrated a driving or power shaft of a starter motor (not shown). Shaft 10 has a portion 12 forming a shoulder 14 and multiple lead helical screw threads or splines 16 formed thereon. Power shaft 10 extends to the right (in the drawing) of the threads or splines 16 having a smooth shaft portion 18.

concentrically mounted on shaft 10 is a first member 28 having an axially-extending portion 30 and a threaded or splined portion 36 to mate with the threads or splines 16 of the power shaft. A second member 38 is disposed intermediate of the threaded portion 16 of the power shaft 10 and the spring retainer 74 held in place by snap ring 76 on the power shaft 10. The second member 38 has an axially-extending annular portion 40 which coopcrates with the axially-extending portion 30 of the first member 28 to retain a plurality of resilient torque-absorbing members 32. The second member axially-extending annulus 40 has a radially-extending portion or finger 31 which extends into arcuate chambers or compartments 33 formed in the first member axially-extending annulus 30. The radial fingers 31 do not engage the inner circumference of the compartments 33.

The resilient members 32 are placed in the compartments 33. The resilient members 32 are typically a rubber or rubber type, at least partially, elastically deformable substance which, when uncompressed (as shown in FIG- URE 2) do not fully occupy the compartment into which they are placed. Those skilled in the art will appreciate that the chambers may be formed in the second member 38 and the radial fingers formed in the first members 30.

A driving clutch member 42 having first torque transmitting teeth 44 formed thereon is slidably journalled on 3,327,8 2l Patented June 27, 1967 straight splines 72 formed on the second members 38. The straight splines 72 are diametrically opposed and are loosely fitted into the matching driving clutch member 42 and splines 75. Radial slots 68 are formed in the second member 38 and are engaged by a split ring or lock ring member 70 which limits the motion of the driving clutch member 42 away from the housing 62 which encloses the resilient members 32 and portions of the first and second members 28 and 38 respectively by abutting a radial lip 67 formed on the driving clutch member.

An annular spring 60 biases the driving clutch member 42 away from the housing 62. A resilient coil spring member 66 is compressively confined between the abutment member 74 and the second member 38.

A two piece driven clutch unit 48 and 50 has a second dentil tooth torque transmitting surface 46 formed on the first driven clutch member 48 for engaging the driving clutch dentil tooth surface 44. A first ramp toothed surface 54 of the first driven clutch member 48 mates with the second ramp toothed surface 56 of the second driven clutch members 50. The first driven clutch member 48 is splined at 52 to the driven shaft 26 and the second driven clutch member is fixedly connected to the driven shaft 20. One driven clutch member can be indexed or rotated on the splines 52 relative to the second driven clutch member to adjust the axial dimension of the assembly and thereby adjust the separation of the first and second torque transmitting teeth 44 and 46. A bolt 78 holds the two part driven clutch in the position desired.

The position of the parts shown in FIGURE 1 represents the non-energized position of the parts prior to a starting cycle. Power shaft 10 is stationary and spring 66 urges the first and second axially-extending members 28 and 38 in a retracted or disengaged position.

When the starting motor (not shown) is energized and begins to accelerate power shaft 10, the inertia of the first and second axially-extending members 28 and 38, the housing 62 and the driving clutch member 42 cause threads 36 to slip on threads 16, inducing relative rotation which causes those members to traverse to the right (as shown in the drawing) so that the driving clutch member 42 can engage the driven clutch members 48 and 50 to drive the shaft 20 of the engine to be started.

As the driving clutch member 42 engages the driven clutch member 48, it is possible that clutch teeth 44 and 46 may abut instead of mesh. If that occurs, annular spring member 60 permits the driving clutch member 42 to move a limited amount relative to the nut member 28 until the driving clutch teeth 44 have rotated sufficiently to fully mesh with the driven clutch teeth 46 when the spring 60 provides a positive engaging force.

When clutch dentil teeth 44 and 46 fully mesh, a deceleration shock of considerable magnitude is transferred to the driving clutch member 42 and would be transferred to the drive shaft 10 of the starting motor, except for the presence of the cylindrical compression members 32 disposed intermediate of the first and second axially-extending members 28 and 38 respectivelyv As driving clutch 42 is rapidly decelerated, the second member 38 is also rapidly decelerated because of the straight spline connection between the member. In the embodiment shown, the.

drive shaft 10 will be rotating in a counterclockwise direction as shown by arrow so in FIGURE 2. Thus, the compressible cylinder members 32 will be compressed between the finger members 31 and the compartments 33 to absorb much of the deceleration energy and later return it to the driving clutch member 42. The members 32 are designed to leave space in the chambers 33 to permit their deformation. The size, elasticity, and type of at least partially elastically deformable members are a matter of design choice.

, 68, lock ring 70 and lip 67 enable the driving clutch member to have a variable radial position so that it will align itself radially relative to the driven shaft 20 to avoid side loads in the driven shaft 20 and driven shaft bearings (not shown). Thus, the present invention is self-aligning, thereby preventing damage to the driven shaft and driven shaft bearings.

When the engine attains a start, driven shaft 20 overspeeds drive shaft causing driven clutch teeth 46 to start to overrun driving clutch teeth 44. This action, in conjunction with the return or disengagement spring 66, causes the driving clutch 42 to be drawn out of contact with the driven clutch member dentils 46. In the overrunning condition, the second axially-extending member 40 is tending to rotate more rapidly in the direction shown by arrow 80 in FIGURE 2, that is, the first axially-extending member. In relative rotation in that direction, finger member 31 makes an uncushioned contact with compartment 33, enabling quick retraction of the driving clutch members from the now overspeeding driven clutch member. Energy absorption in the overspeeding condition is undesirable and avoided by the present invention.

One use of the present invention is as a turbine engine starter. In that type of application, it is especially desirable that energy absorption be in only one direction. It is also especially desirable that self-alignment capability is present since the motor shaft may be turning at 40,000 revolutions per minute when non-uniform bearing loads readily cause shaft or hearing failure.

It is also highly desirable that all high mass starter elements remain on the low speed starter motor side of the starter gearing to keep hearing loads as low as possible. This object is accomplished by the present invention because in the overspeed condition only the lightweight twopiece driven clutch is connected to the driven shaft 20.

It should also be noted that the present invention consists of a relatively few parts which need not be carefully machined so that material and processing costs are low.

It can readily be appreciated that the present invention achieves its stated objects. Thus, the present invention provides a highly reliable, yet low cost, starter drive. Although a specific embodiment of the present invention has been shown and described, those skilled in the art will appreciate that changes can be made in the design and location of the starter drive parts without departing from the scope and spirit of the present invention.

I claim:

1. An engine starter drive comprising:

a drive shaft member having a helical spline formed thereon;

a first axially-extending annular member threadedly received on said drive shaft splines;

a second axially-extending annular member slidably journalled on said drive shaft;

a plurality of compression members disposed intermediate of said first and second axially-extending annular member to absorb start up torque loads on said drive shaft;

said second axially-extending member having substantially diametrically-opposed straight splines;

a driving clutch member having first torque transmitting teeth slida'bly journalled on said second axiallyextending member straight splines;

a plurality of radial slots formed in said straight splines;

a lock ring member fitted into said radial slots to retain said driving clutch member on said second axiallyextending member;

a housing means enclosing said first and second axiallyextending members and said plurality of rubber cylinders;

an annular spring member compressively confined between said housing meansand said driving clutch member;

an abutment member fastened to the driven end of the drive shaft;

a coil spring member compressively confined between said second axially-extending member and said abutment means; and

a driven clutch member having second torque transmitting teeth complementing said first torque transmitting teeth.

2. The starter drive in claim 1 including further:

a plurality of arcuate cavities formed in said first axially-extending member:

a plurality of radially-extending members formed on said second axially-extending members adapted to be movably disposed in said cavities; and

a plurality of cylindrical compression members disposed intermediate of the cavity and said radiallyextending members.

3. An engine starter drive comprising:

a drive shaft member having a helical spline formed thereon;

spline;

a slide member slidably journalled on said drive shaft having straight splines on the outer circumference thereof;

said nut member and said slide member forming a plurality of compartments;

a plurality of resilient members disposed in said compartments to absorb torque loads applied from said drive shaft to said slide member;

a housing means enclosing said nut member and said slide member;

a driving clutch means having first torque transmitting means thereon slidably journalled on said slide member straight splines;

a first spring means compressively confined between said housing means and said driving clutch means;

a second spring means biasing said slide member towards said nut member; and

a driven clutch means having second torque transmitting means thereon adapted to engage said driving clutch torque transmitting means.

4. The starter drive in claim 3 wherein:

said nut member and said slide member are rotatable relative to each other;

one of said members having a plurality of arcuate chambers and the other of said members having a plurality of radially-extending members; and said resilient members are disposed in said compartments in such a manner as to be compressively confined therein when torque is applied to said driving clutch.

5. The starter drive in claim 4 wherein said resilient means comprises:

a cylindrical resiliently-deformable member having an uncompressed volume less than that of said compartments. 6. The starter drive in claim 3 including further: radial slot means formed in said slide member straight splines; ring means engaging said slot means; and a radiallyy-extending portion formed in said nut end of said driving clutch means away from said slide member.

References Cited UNITED STATES PATENTS 2,244,220 6/1941 Schauer 747 2,850,906 9/ 1958 Mendenhall 747 3,071,013 1/1963 Antonidis et a1 747 3,114,270 12/1963 Buxton et al 192-42 X 3,187,870 6/1965 Sabatini 19242 X MARK NEWMAN, Primary Examiner.

A. T. MCKEON, Assistant Examiner. 

3. AN ENGINE STARTER DRIVE COMPRISING: A DRIVE SHAFT MEMBER HAVING A HELICAL SPLINE FORMED THEREON; A NUT MEMBER THREADEDLY RECEIVED ON SAID DRIVE SHAFT SPLINE; A SLIDE MEMBER SLIDABLY JOURNALLED ON SAID DRIVE SHAFT HAVING STRAIGHT SPLINES ON THE OUTER CIRCUMFERENCE THEREOF; SAID NUT MEMBER AND SAID SLIDE MEMBER FORMING A PLURALITY OF COMPARTMENTS; A PLURALITY OF RESILIENT MEMBERS DISPOSED IN SAID COMPARTMENTS TO ABSORB TORQUE LOADS APPLIED FROM SAID DRIVE SHAFT TO SAID SLIDE MEMBER; A HOUSING MEANS ENCLOSING SAID NUT MEMBER AND SAID SLIDE MEMBER; A DRIVING CLUTCH MEANS HAVING FIRST TORQUE TRANSMITTING MEANS THEREON SLIDABLY JOURNALLED ON SAID SLIDE MEMBER STRAIGHT SPLINES; A FIRST SPRING MEANS COMPRESSIVELY CONFINED BETWEEN SAID HOUSING MEANS AND SAID DRIVING CLUTCH MEANS; A SECOND SPRING MEANS BIASING SAID SLIDE MEMBER TO WARDS SAID NUT MEMBER; AND A DRIVEN CLUTCH MEANS HAVING SECOND TORQUE TRANSMITTING MEANS THEREON ADAPTED TO ENGAGE SAID DRIVING CLUTCH TORQUE TRANSMITTING MEANS. 